1. Field of the Invention
The present invention generally relates to optical protection switching architectures. More particularly, the present invention is directed to an optical cross-connect system utilizing 4xc3x974 switching matrices for providing self-healing from any single point of failure.
2. Technical Background
In the rapid development of optical communication systems, networking architectures have become increasingly complex. Ring topologies have arisen to provide a number of networking elements with the ability to both listen and transmit on optical channels within the optical ring. In such a ring topology, consecutive nodes are connected by point-to-point links which are arranged to form a single closed path or ring. Information is transmitted from node to node around the ring, and the interface at each node is an active device that has the ability to create and accept messages. The interface serves not only as a user attachment point but also as an active repeater for re-transmitting messages that are addressed to other nodes.
A number of implementation considerations must be taken into account when configuring a ring network. First, rings must be physically arranged so that all nodes are fully connected. Whenever a node is added to support new devices, transmission lines have to be placed between this node and its two nearby, topologically adjacent nodes. A break in any line, the failure of a node, or adding a new node threatens to disrupt network operation. A variety of steps can be taken to circumvent these problems, although this generally increases the complexity of the ring interface electronics as well as the associated costs.
The American National Standards Institute (ANSI) has released a collection of standards for synchronous optical networks (SONET""s) to address a growing bandwidth problem in the wide area network (WAN) environment. These standards provide signaling protocols for various types of optical networks but fail to address optical cross-connect systems with any specificity. Another problem with structuring a bidirectional optical ring around SONET standards, is the possibility of transmitting data which is not SONET based. For example, gigabyte Ethernet signals transmitted to digital clients often do not fall within SONET standards. Thus, it is desirable to provide a bidirectional optical ring architecture with the flexibility of operating within or out of SONET protocols. It is also desirable to provide improved protection against single point failures and network changes.
The above and other objects are provided by an optical cross-connect system having a pair of 4xc3x974 optical switching matrices. The switching matrices route working traffic and redundant protection traffic between a plurality of clients and an optical ring. The optical cross-connect system also has a client interface for transporting the working traffic and the protection traffic between the switching matrices and the clients. The optical cross-connect system further includes a ring interface for transporting the working traffic and the protection traffic between the switching matrices and the optical ring. The switching matrices are structured so that protection is provided from single point failures by electrical switching at the client location. This significantly reduces the need for optical switching within the switching matrices. The 4xc3x974 architecture of the matrices provides a fundamental building block which allows ultimate flexibility in design of optical rings.
It is to be understood that both the foregoing general description and the following detailed description are merely exemplary of the invention, and are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute part of this specification. The drawings illustrate various features and embodiments of the invention, and together with the description serve to explain the principles and operation of the invention.